Real-world analog signals such as temperature, pressure, sound, or images are routinely converted to a digital representation that can be easily processed in modern digital systems. In many systems, this digital information must be converted back to an analog form to perform some real-world function. The circuits that perform this step are digital-to-analog converters (DACs), and their outputs may be used to drive a variety of devices. Loudspeakers, video displays, motors, mechanical servos, radio frequency (RF) transmitters, and temperature controls are just a few diverse examples. DACs are often incorporated into digital systems in which real-world signals are digitized by analog-to-digital converters (ADCs), processed, and then converted back to analog form by DACs. In these systems, the performance required of the DACs will be influenced by the capabilities and requirements of the other components in the system.
Often, a DAC system includes multiple DACs, where outputs of the different DACs need to be synchronized to be within tight timing tolerances as specified by a particular application. Typically synchronicity of less than a single clock cycle of a DAC clock is required, which, in turn, means that it may be very difficult to achieve synchronization at high clock speeds since the duration of a clock cycle is inversely proportional to the clock speed. For example, with a 5 gigahertz (GHz) clock, the clock cycle is 200 picoseconds (ps) and synchronization error up to 200 ps may be acceptable, but the same application implemented with a 10 GHz clock may require that the synchronization error is less than 100 ps because that's the clock cycle at 10 GHz.
Improvements could be made with respect to synchronizing DAC outputs of multiple DACs in a system, in particular in fast clock systems.